Persistent Alkyne-Bridged Bis-Trityl Diradicaloids with an Open-Shell Ground State
Abstract
Organic singlet diradicaloids are of interest for spintronics, singlet fission, and quantum information science because of their electronic and magnetic properties. However, the synthesis of persistent diradicaloids with high diradical character remains a challenge. Herein, we report the synthesis of three novel alkyne-bridged diradicaloids based on a tetrathiaarylmethyl (trityl) radical. Electron Paramagnetic Resonance spectroscopy and magnetic susceptibility measurements were used to determine the spin-spin exchange interaction J in all three compounds, revealing narrow singlet-triplet gaps of -1 kcal/mol, -0.4 kcal/mol, and -0.05 kcal/mol for 1 •• , 2 •• , and 3 •• , respectively. DFT calculations support the singlet open-shell nature of the ground state in all three diradicaloids and yield a diradical character y 0 of 0.47, 0.53, and 0.76 for 1 •• , 2 •• , and 3 •• , respectively. Furthermore, low-energy absorption bands at 780 nm for 1 •• and 2 •• and at 500 nm for 3 •• show the transition between the open-shell ground state and a closed-shell cumulenic state. In addition, the reactivity of all three compounds towards oxygen is rationalized based on the spin-spin interaction. Lastly, since the molecules share similar geometries, J is found to be in inverse correlation to y 0 .This study thereby provides extensive insight into the structural relations between polyynic and cumulenic states, and the stability of tritylbased diradicaloids.
Related
- Interplay of Bridge Topology and Conformation in Phenylene‐Bridged Trityl Diradicals
- Internal conversion in functionalized poly-chlorinated trityl radicals can be tuned by a characteristic high-frequency mode
- Beyond Radical Emitters: Hot‐Exciton Electroluminescence From Singlet Diradicaloids
- Cobalt-catalyzed alkyne migratory hydroboration to access β-alkenylboronates via catalytic zipper-like alkyne translocation
- Auto‐Click Synthesis of a Copper(I) –N ‐Heterocyclic Carbene Porous Organic Polymer and Its Transmetalation to Palladium(II) for Azide–Alkyne Cycloaddition and Cross‐Coupling Reactions
BibTeX
@misc{westhofen2026persistent,
title = {{Persistent Alkyne-Bridged Bis-Trityl Diradicaloids with an Open-Shell Ground State}},
author = {Lars Westhofen and Andrea Pellegrini and Stefan Grimme and Olav Schiemann},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009495/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009495/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Persistent Alkyne-Bridged Bis-Trityl Diradicaloids with an Open-Shell Ground State
AU - Lars Westhofen
AU - Andrea Pellegrini
AU - Stefan Grimme
AU - Olav Schiemann
PY - 2026
DA - 2026/09/27
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009495/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009495/v1
AB - Organic singlet diradicaloids are of interest for spintronics, singlet fission, and quantum information science because of their electronic and magnetic properties. However, the synthesis of persistent diradicaloids with high diradical character remains a challenge. Herein, we report the synthesis of three novel alkyne-bridged diradicaloids based on a tetrathiaarylmethyl (trityl) radical. Electron Paramagnetic Resonance spectroscopy and magnetic susceptibility measurements were used to determine the spin-spin exchange interaction J in all three compounds, revealing narrow singlet-triplet gaps of -1 kcal/mol, -0.4 kcal/mol, and -0.05 kcal/mol for 1 •• , 2 •• , and 3 •• , respectively. DFT calculations support the singlet open-shell nature of the ground state in all three diradicaloids and yield a diradical character y 0 of 0.47, 0.53, and 0.76 for 1 •• , 2 •• , and 3 •• , respectively. Furthermore, low-energy absorption bands at 780 nm for 1 •• and 2 •• and at 500 nm for 3 •• show the transition between the open-shell ground state and a closed-shell cumulenic state. In addition, the reactivity of all three compounds towards oxygen is rationalized based on the spin-spin interaction. Lastly, since the molecules share similar geometries, J is found to be in inverse correlation to y 0 .This study thereby provides extensive insight into the structural relations between polyynic and cumulenic states, and the stability of tritylbased diradicaloids.
ER -